The vulnerabilities are reported to affect PHP versions 4.4.0 and prior. Users are advised to update to version 4.4.1 (release notes here). Most of this batch of PHP security vulnerabilities (summary) were discovered by Stefan Esser, of the Hardened-PHP Project, which has published a series of advisories here.

The security bugs described by the Hardened-PHP Project are yet to be developed into s'kiddie friendly exploits. But the past appearance of PHP-targeting worms, and the damage they caused, really ought to prompt the rapid deployment of security updates.